Synthetic polymers are used in many textile applications to replace natural textile materials such as wool and cotton. Synthetic polymers are also used for other textile-related applications such as insulation layers in clothing, particularly clothing for outdoor use in colder weather, and for bulking properties in pillows and other such products in which these properties are alternatively provided by natural materials such as feathers or by synthetic foam materials.
The starting product for almost all synthetic textile materials is a liquid polymer that is extruded in the form of a thin filament of the material. Such filaments have some immediate uses such as fishing line. In textile applications, however, synthetic filaments and the fibers and yarns made from them should desirably provide properties similar to those of natural fibers such as wool or cotton. In order to provide such properties, synthetic filaments must be textured before being formed into yarns and fabrics. As is well understood in the textile industry, texturing can comprise crimping, looping, or otherwise modifying continuous filaments to increase their cover, resilience, abrasion resistance, warmth, insulation properties, and moisture absorption, or to provide a somewhat different surface texture.
Typical texturing methods include false twist texturing, mechanical texturing such as edge crimping or gear crimping, air jet crimping, knit-de-knit crimping, and the stuffer box method. In quite logical fashion, the resulting characteristics of the textured filament reflects the texturing method used. Thus, textured filaments can take the form of entangled filaments, multifilament coils, monofilament coils, stuffer box crinkles, knit-de-knit crinkles, or core-bulked filaments. Each of these has its own particular properties, advantages, and disadvantages.
Among these various types of textured filaments, coils are preferred for certain applications such as cushions and insulation. Coiled filaments tend to give more volume and fewer sharp bends, "zig-zags," or "knees". Generally speaking, coiled filaments, and the yarns made from them, take on a coil or spiral configuration that is somewhat more three dimensional than other textured filaments and thus are preferred for many bulking applications, including those mentioned above.
Typical methods for coiling filaments include false twisting or edge crimping, both of which techniques are well-known to those of ordinary skill in the art, and will not be otherwise further described herein.
Both of these methods have various advantages and disadvantages in producing coiled yarns. For example, false twist coiling requires a conventional false twist winding system, while an edge crimp method requires the mechanical devices necessary to physically produce the crimp.
Alternatively, coiled filaments can be formed from bilateral fibers that coil following further processing. Traditionally, bilateral fibers are formed from two different generic fibers or variants of the same generic fiber extruded in a side-by-side relationship. Although side-by-side or "bicomponent" spinning offers certain advantages, it also is a relatively demanding process that requires more complex spinning equipment and thus is advantageously avoided where unnecessary.
Therefore, it is an object of the present invention to provide a method of coiling filament, particularly polyester filament, to produce a coiled filament from which appropriate yarns or bulk material can be produced. Furthermore, it is an object of the invention to do so without the requirement of false twisting, mechanical crimping, or bicomponent spinning.